Field
Embodiments described herein relate to apparatus and methods of thermal processing. More specifically, apparatus and methods described herein relate to laser thermal treatment of semiconductor substrates.
Description of the Related Art
Thermal processing is commonly practiced in the semiconductor industry. Semiconductor substrates are subjected to thermal processing in the context of many transformations, including doping, activation, and annealing of gate source, drain, and channel structures, siliciding, grain growth, crystallization, oxidation, and the like. Over the years, techniques of thermal processing have progressed from simple furnace baking, to various forms of increasingly rapid thermal processing such as rapid thermal processing (RTP), spike annealing, and laser annealing.
Conventional laser annealing processes use laser emitters that may be semiconductor, excimer, gas, or solid state lasers with optics that focus, defocus, or variously image the laser light into a predetermined shape. One approach is to focus the laser onto a rectangle that generally corresponds to one or more integrated circuit dies formed on a substrate. Each die is processed by pulsing the laser, and stepping die by die across the substrate. The surface of the substrate may have various optical absorbances, leading to non-uniform temperatures across the surface. This differential heating creates a difference in process results known as the “pattern effect” as it often follows the die pattern on the substrate. The pattern effect has become one of the largest problems for process integration and the acceptance of laser processing tools into production. Thus, there is a need for new apparatus and methods for thermal processing of semiconductor substrates.